Downregulation of Pdcd4 by mir-21 facilitates glioblastoma proliferation in vivo

Department of Pediatrics, Norris Cotton Cancer Center, Dartmouth Medical School, Lebanon, NH 03755, USA.
Neuro-Oncology (Impact Factor: 5.56). 06/2011; 13(6):580-90. DOI: 10.1093/neuonc/nor033
Source: PubMed


MicroRNAs (miRNAs) are small, noncoding RNAs that play a critical role in developmental and physiological processes and are implicated in the pathogenesis of several human diseases, including cancer. They function by regulating target gene expression post-transcriptionally. In this study, we examined the role of oncogenic mir-21 in the pathogenesis of glioblastoma, the most aggressive form of primary brain tumor. We have previously reported that mir-21 is expressed at higher levels in primary glioblastoma-tissue and glioblastoma-derived cell lines than in normal brain tissue. We demonstrate that downregulation of mir-21 in glioblastoma-derived cell lines results in increased expression of its target, programmed cell death 4 (Pdcd4), a known tumor-suppressor gene. In addition, our data indicate that either downregulation of mir-21 or overexpression of its target, Pdcd4, in glioblastoma-derived cell lines leads to decreased proliferation, increased apoptosis, and decreased colony formation in soft agar. Using a glioblastoma xenograft model in immune-deficient nude mice, we observe that glioblastoma-derived cell lines in which mir-21 levels are downregulated or Pdcd4 is over-expressed exhibit decreased tumor formation and growth. Significantly, tumors grow when the glioblastoma-derived cell lines are transfected with anti-mir-21 and siRNA to Pdcd4, confirming that the tumor growth is specifically regulated by Pdcd4. These critical in vivo findings demonstrate an important functional linkage between mir-21 and Pdcd4 and further elucidate the molecular mechanisms by which the known high level of mir-21 expression in glioblastoma can attribute to tumorigenesis--namely, inhibition of Pdcd4 and its tumor-suppressive functions.

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    • "GBM-derived cell lines treated with anti-miR-21 had reduced proliferation and also exhibited enhanced apoptosis, compared with untreated controls. In addition, cell lines in which miR-21 levels were inhibited displayed decreased anchorage-independent growth, whereas GBM-derived cell lines expressing PDCD4 showed increased apoptosis and diminished anchorage-independent growth [43]. miR-21 seems to regulate drug resistance in various cancers, and therefore the use of miR- 21 inhibitors may function as an effective approach for reversing drug resistance in canmiRNA expression profiles in pediatric glioblastoma multiforme 240 Am J Cancer Res 2015;5(1):231-242 cer cells. "
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    ABSTRACT: Various signal transduction pathways seem to be involved in chemoresistance mechanism of glioblastomas (GBMs). miR-21 is an important oncogenic miRNA which modulates drug resistance of tumor cells. We analyzed the expression of 5 miRNAs, previously found to be dysregulated in high grade gliomas, in 9 pediatric (pGBM) and in 5 adult (aGBM) GBMs. miR-21 was over-expressed, with a significant difference between pGBMs and aGBMs represented by a 4 times lower degree of expression in the pediatric compared to the adult series (p = 0.001). Doxorubicin (Dox) seems to be an effective anti-glioma agent with high antitumor activity also against glioblastoma stem cells. We therefore evaluated the chemosensitivity to Dox in 3 GBM cell lines (A172, U87MG and T98G). Dox had a cytotoxic effect after 48 h of treatment in A172 and U87MG, while T98G cells were resistant. TUNEL assay verified that Dox induced apoptosis in A172 and U87MG but not in T98G. miR-21 showed a low basal expression in treated cells and was over-expressed in untreated cells. To validate the possible association of miR-21 with drug resistance of T98G cells, we transfected anti-miR-21 inhibitor into the cells. The expression level of miR-21 was significantly lower in T98G transfected cells (than in the parental control cells). Transfected cells showed a high apoptotic rate compared to control after Dox treatment by TUNEL assay, suggesting that combined Dox and miR-21 inhibitor therapy can sensitize GBM resistant cells to anthracyclines by enhancing apoptosis.
    American Journal of Cancer Research 01/2015; 5(1):231-42. · 4.17 Impact Factor
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    • "It has been reported that miRNA-21 plays a vital role in keratinocyte migration and in re-epithelialization during wound healing, directly targeting TIMP3 in vitro and in vivo [25]. By down-regulating PDCD4, miRNA-21 contributes to glioblastoma proliferation while its inhibition induced apoptosis and decreased cell cycle progression, down-regulating EGFR, activated akt, cyclin D and bcl-2 in vitro and in vivo suggesting an important therapeutic potential of miRNA-21 [26], [27]. Thus, the fact that miRNA-21 is frequently elevated in most malignancies and its in vivo knockdown suppresses tumorous potential, suggests that its high levels are essential for promoting pathological cell growth. "
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    ABSTRACT: Hepatitis B viral infection-induced hepatocellular carcinoma is one of the major problems in the developing countries. One of the HBV proteins, HBx, modulates the host cell machinery via several mechanisms. In this study we hypothesized that HBV enhances cell proliferation via HBx-induced microRNA-21 in hepatocellular carcinoma. HBx gene was over-expressed, and miRNA-21 expression and cell proliferation were measured in Huh 7 and Hep G2 cells. miRNA-21 was over-expressed in these cells, cell proliferation and the target proteins were analyzed. To confirm the role of miRNA-21 in HBx-induced proliferation, Hep G cells (a cell line that expresses HBV stably) were used for miRNA-21 inhibition studies. HBx over-expression enhanced proliferation (3.7- and 4.5-fold increase; n = 3; p<0.01) and miRNA-21 expression (24- and 36-fold increase, normalized with 5S rRNA; p<0.001) in Huh 7 and Hep G2 cells respectively. HBx also resulted in the inhibition of miRNA-21 target proteins, PDCD4 and PTEN. miRNA-21 resulted in a significant increase in proliferation (2- and 2.3-fold increase over control cells; p<0.05 in Huh 7 and Hep G2 cells respectively) and decreased target proteins, PDCD4 and PTEN expression. Anti-miR-21 resulted in a significant decrease in proliferation (p<0.05) and increased miRNA-21 target protein expression. We conclude that HBV infection enhances cell proliferation, at least in part, via HBx-induced miRNA-21 expression during hepatocellular carcinoma progression.
    PLoS ONE 03/2014; 9(3):e91745. DOI:10.1371/journal.pone.0091745 · 3.23 Impact Factor
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    • "In a glioma mouse model important decrease in growth tumor was observed after inhibiting miR-10b by intratumoral antimiR injection [101]. Other animal studies also reported tumor reduction following inhibition of oncogenic miR-21 in GBM [116]. MiR-21 and miR-195 down regulation in GBM culture cells sensitize cells to treatment with 5-fluorouracil and temozolomide [117, 118]. "
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    ABSTRACT: High grade gliomas represent one of the most aggressive and treatment-resistant types of human cancer, with only 1-2 years median survival rate for patients with grade IV glioma. The treatment of glioblastoma is a considerable therapeutic challenge; combination therapy targeting multiple pathways is becoming a fast growing area of research. This review offers an up-to-date perspective of the literature about current molecular therapy targets in high grade glioma, that include angiogenic signals, tyrosine kinase receptors, nodal signaling proteins and cancer stem cells related approaches. Simultaneous identification of proteomic signatures could provide biomarker panels for diagnostic and personalized treatment of different subsets of glioblastoma. Personalized medicine is starting to gain importance in clinical care, already having recorded a series of successes in several types of cancer; nonetheless, in brain tumors it is still at an early stage.
    Current Proteomics 09/2013; 10(3):246-260. DOI:10.2174/1570164611310030007 · 0.64 Impact Factor
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